April
12
Culturing Organisms
Batch Culture
- Organism in housed in a enclosed vessel
- Cannot grow exponentially
- Nutrient concentration affects both growth rate and growth yield
- Low concentrations- Growth rate is submaximal since nutrients cannot be transport into the cell fast enough to satisfy metabolic demand
- High concentrations- maximal growth rate may be obtained, but the cell density can continue to increase in proportion to the concentration of nutrients in the medium
- Growth Curve describes the growth cycle
- Lag Phase
- Exponential phase
- Stationary Phase
- Death Phase
- Lag Phase
- Brief or extended time frame
- Inoculum taken from old culture
- Lag is present due to cells being deprived of key nutrients
- Lag present if inoculum is low of viability(few live cells)
- Lag is present if cells are damaged but not killed by stressor(Temperature, radiation, toxic chemicals)
- Lag is observed when microbial culture is transferred from a rich to poor culture
- Exponential Phase
- Cell population doubles at regular intervals for a brief or extended period
- Depends on available resources and other factors
- Cells are in their healthiest state
- Rate of exponential growth is influenced by environmental conditions( temperature, composition of culture medium) and genetic characteristics
- Prokaryotes grow faster than eukaryotes
- Small eukaryotes grow faster than larger ones
- Cell population doubles at regular intervals for a brief or extended period
- Stationary Phase
- No net increase or decrease in cell number and thus the growth rate of the population is zero.
- Energy metabolism and biosynthetic processes may continue at reduced rate
- Death Phase
- Rate of cell death is slower than rate of exponential growth and viable cells remain in culture for months or years
- Cryptic Growth- Exponential and Death phases balance each other out